UNDERSTANDING THE SHIPPING AND INSHORE WATERS FORECASTS

The Shipping Forecast and Inshore Waters Forecast both use a standard and abbreviated format to pass a lot of information in a short period of time - by knowing what's being said and in what order (always the same) it's possible to gain an understanding of the conditions, even in poor reception areas if listening to the forecast on marine VHF. The terms used are standardised.

As well as marine VHF, weather bulletins for shipping are broadcast daily on BBC Radio 4. The bulletins consist of a gale warning summary, general synopsis, sea-area forecasts and coastal station reports. In addition, gale warnings are broadcast at the first available programme break after receipt. If this does not coincide with a news bulletin, the warning will be repeated after the next news bulletin.

Other sources of weather information are linked from the Almanac / Weather page, as is information on MSI schedules for forecasts on Marine VHF.

This is a general overview - at 1300 there is a low pressure area to the west of Rockall - with a barometric pressure of 987. It's expected to move NE to Bailey with a barometric pressure of 983 by 1300 Sunday 3 July.

(Low pressure tends to produce unsettle, poor weather - as I write this, it is!). The difference between the pressures is of interest - in this case, the relative similarity tells us that the conditions won't change much.

For the sea areas Viking, North Utsire and South Utsire. These are located NE of UK.

Wind from the Southeast, windspeed Beaufort force 4 or 5, increasing to force 6 or 7, veering / changing in a clockwise direction to the South, force 4 or 5 but not within the next 12 hours.

Occasional rain.

Visibility will be good / more than 5 nautical miles, but with patches of fog and becoming moderate / between 2 and 5 nautical miles or poor / between 1,000 metres and 2 nautical miles.

A bit easier to understand than the Shipping Forecast, the Inshore Waters forecast always says what the information relates to. In this case, the wind is coming from the West, windspeed Beaufort force 3 or 4 but likely to vary. In the area near Rattrray Head it'll become Northwest 4 by tomorrow morning.

Visibility will be moderate / between 2 and 5 nautical miles or good / more than 5 nautical miles, but with patches of fog, and poor / between 1,000 metres and 2 nautical miles in the Moray Firth area.

Term used

Gale Warnings

Gale

Winds of at least Beaufort Scale force 8 (34-40 knots) or gusts reaching 43-51 knots

Severe gale

Winds of force 9 (41-47 knots) or gusts reaching 52-60 knots

Storm

Winds of force 10 (48-55 knots) or gusts reaching 61-68 knots

Violent storm

Winds of force 11 (56-63 knots) or gusts of 69 knots or more

Hurricane force

Winds of force 12 (64 knots or more)

Note: The term used is 'hurricane force'; the term 'hurricane' on its own means a true tropical cyclone, not experienced in British waters.

Timescales

Imminent

Expected within six hours of time of issue

Soon

Expected within six to 12 hours of time of issue

Later

Expected more than 12 hours from time of issue

Pressure change of 0.1 to 1.5 hPa in the preceding three hours

Pressure change of 1.6 to 3.5 hPa in the preceding three hours

Pressure change of 3.6 to 6.0 hPa in the preceding three hours

Pressure change of more than 6.0 hPa in the preceding three hours

Pressure has been falling (rising) or steady in the preceding three hours, but at the time of observation was definitely rising (falling)

Note: For those more familiar with the millibar, 1 hPa = 1 mb

Wind direction

Indicates the direction from which the wind is blowing - see this Factsheet on understanding wind direction.

Becoming cyclonic

Indicates that there will be considerable change in wind direction across the path of a depression within the forecast area

Veering

The changing of the wind direction clockwise, e.g. SW to W

Backing

The changing of the wind in the opposite direction to veering (anticlockwise), e.g. SE to NE